Half-life of first order process

A reactant undergoes a dissociation reaction A r arrow 2B which follows first order kinetics. The initial concentration of reactant A is .4000 M and after 75.00 hr the concentration of A decreases to 0.0816 M. Determine the half-life of the first order process.

There must be a simple equation for this, but my textbook must assume we would already know it. I can't find it anywhere! Thanks

Solution Summary

This solution is provided in 41 words in an attached .doc file. It provides a simple, brief calculation for finding half-life of a process.